U.S. patent application number 11/473358 was filed with the patent office on 2006-12-28 for polypropylene having reduced residual metals.
This patent application is currently assigned to Fina Technology, Inc.. Invention is credited to Kenneth P. Blackmon, Mark C. Douglass, Kevin P. McGovern, Mark Miller, Joseph D. Thorman.
Application Number | 20060293504 11/473358 |
Document ID | / |
Family ID | 37595802 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060293504 |
Kind Code |
A1 |
Blackmon; Kenneth P. ; et
al. |
December 28, 2006 |
Polypropylene having reduced residual metals
Abstract
Polymerization processes are described herein. The
polymerization processes generally include introducing a catalyst
system to a reaction zone, introducing an olefin monomer to the
reaction zone, contacting the olefin monomer with the catalyst
system to form a polyolefin and contacting the polyolefin with a
quench agent, wherein the quench agent is at least partially
soluble in the olefin monomer.
Inventors: |
Blackmon; Kenneth P.;
(Houston, TX) ; Douglass; Mark C.; (League City,
TX) ; McGovern; Kevin P.; (Houston, TX) ;
Miller; Mark; (Houston, TX) ; Thorman; Joseph D.;
(League City, TX) |
Correspondence
Address: |
FINA TECHNOLOGY INC
PO BOX 674412
HOUSTON
TX
77267-4412
US
|
Assignee: |
Fina Technology, Inc.
Houston
TX
|
Family ID: |
37595802 |
Appl. No.: |
11/473358 |
Filed: |
June 22, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60693298 |
Jun 23, 2005 |
|
|
|
Current U.S.
Class: |
528/495 |
Current CPC
Class: |
C08F 6/02 20130101; C08L
23/10 20130101; C08L 23/14 20130101; C08F 2500/12 20130101; C08F
6/02 20130101; C08F 6/02 20130101; C08F 110/06 20130101; C08F
110/06 20130101 |
Class at
Publication: |
528/495 |
International
Class: |
C08F 6/00 20060101
C08F006/00 |
Claims
1. A polymerization process comprising: introducing a catalyst
system to a reaction zone; introducing an olefin monomer to the
reaction zone; contacting the olefin monomer with the catalyst
system to form a polyolefin; and contacting the polyolefin with a
quench agent, wherein the quench agent is at least partially
soluble in the olefin monomer.
2. The process of claim 1, wherein the olefin monomer comprises
propylene.
3. The process of claim 2, wherein the quench agent comprises
isopropanol.
4. Polypropylene formed from the process of claim 2.
5. The process of claim 2 further comprising contacting the
polyolefin with a wash agent comprising propylene.
6. The process of claim 1 further comprising contacting the
polyolefin with a wash agent comprising the olefin monomer, wherein
the wash agent contacts the polyolefin in a flow direction that is
countercurrent to a flow direction of the polyolefin.
7. The process of claim 1, wherein the catalyst system comprises a
Ziegler-Natta catalyst system.
8. The process of claim 7 further comprising contacting the
Ziegler-Natta catalyst system with a cocatalyst, wherein the
cocatalyst comprises an organoaluminum compound.
9. The process of claim 1 further comprising contacting the
catalyst system with a cocatalyst, wherein the cocatalyst comprises
triethyl aluminum.
10. The process of claim 9, wherein the cocatalyst contacts the
catalyst system at a cocatalyst ratio of from about 0.3 to about
0.7.
11. A polymer article formed from the process of claim 1, wherein
the polymer article is selected from food packaging, cigarette
wrapping, stationary lamination, shrink warp and industrial
laminates.
12. The process of claim 1, wherein the reaction zone comprises a
loop reactor.
13. A process for reducing a residual metal level in polypropylene
comprising: providing a first polypropylene, wherein the first
polypropylene comprises a first aggregate residual metal level that
is at least 60 ppm; contacting the first polypropylene with a
quench agent comprising isopropanol to form a second polypropylene;
and recovering the second polypropylene, wherein the second
polypropylene comprises a second aggregate residual metal level
that is about 40 ppm or less.
14. The process of claim 13, wherein the first aggregate residual
metal level is formed of residual metals comprising aluminum,
magnesium, titanium or combinations thereof.
15. The process of claim 13 further comprising contacting the
second polypropylene with a wash agent comprising propylene monomer
to form a third polypropylene.
16. The process of claim 15, wherein the third polypropylene
comprises an aluminum residual metal level that is about 32 ppm or
less.
17. The process of claim 13, wherein the first and second aggregate
residual metal levels comprise a first and second aluminum residual
level.
18. The process of claim 17, wherein the second aluminum residual
level is less than about 40 ppm.
19. The process of claim 17, wherein the second aluminum residual
level is less than about 25 ppm.
20. A polymer article formed from the polypropylene of claim
13.
21. An opaque film formed from the polypropylene of claim 13.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/693,298, filed Jun. 23, 2005.
FIELD
[0002] Embodiments of the present invention generally relate to
polyolefins. In particular, embodiments of the present invention
generally relate to polyolefins having reduced residual metal or
catalyst system components levels.
BACKGROUND
[0003] Polymerization processes generally include contacting
monomers with a catalyst system to form polymers.
[0004] Unfortunately, the formed polymers include a level of metals
resulting from catalyst system residues (i.e., residual level.) For
example, these residues may include aluminum, magnesium or
titanium, for example. While the level of residues may be
acceptable for some applications, certain applications require a
residual level that is lower than that achieved by conventional
processes.
[0005] Therefore, a need exists to develop a polymerization process
resulting in polymers having reduced residual levels.
SUMMARY
[0006] Embodiments of the present invention include polymerization
processes. The polymerization processes generally include
introducing a catalyst system to a reaction zone, introducing an
olefin monomer to the reaction zone, contacting the olefin monomer
with the catalyst system to form a polyolefin and contacting the
polyolefin with a quench agent, wherein the quench agent is at
least partially soluble in the olefin monomer.
[0007] Embodiments further include processes for reducing a
residual metal level in polypropylene. The processes generally
include providing a first polypropylene, wherein the first
polypropylene includes a first aggregate residual metal level that
is at least 60 ppm and contacting the first polypropylene with a
quench agent to form a second polypropylene. The second
polypropylene generally includes a second aggregate residual metal
level that is about 40 ppm or less.
DETAILED DESCRIPTION
Introduction and Definitions
[0008] A detailed description will now be provided. Each of the
appended claims defines a separate invention, which for
infringement purposes is recognized as including equivalents to the
various elements or limitations specified in the claims. Depending
on the context, all references below to the "invention" may in some
cases refer to certain specific embodiments only. In other cases it
will be recognized that references to the "invention" will refer to
subject matter recited in one or more, but not necessarily all, of
the claims. Each of the inventions will now be described in greater
detail below, including specific embodiments, versions and
examples, but the inventions are not limited to these embodiments,
versions or examples, which are included to enable a person having
ordinary skill in the art to make and use the inventions when the
information in this patent is combined with available information
and technology.
[0009] Various terms as used herein are shown below. To the extent
a term used in a claim is not defined below, it should be given the
broadest definition persons in the pertinent art have given that
term as reflected in printed publications and issued patents.
Further, unless otherwise specified, all compounds described herein
may be substituted or unsubstituted and the listing of compounds
includes derivatives thereof.
[0010] The term "activity" refers to the weight of product produced
per weight of the catalyst used in a process per hour of reaction
at a standard set of conditions (e.g., grams product/gram
catalyst/hr).
Catalyst Systems
[0011] Catalyst systems useful for polymerizing olefin monomers
include any catalyst system known to one skilled in the art. For
example, the catalyst system may include metallocene catalyst
systems, single site catalyst systems, Ziegler-Natta catalyst
systems or combinations thereof, for example. A brief discussion of
such catalyst systems is included below, but is in no way intended
to limit the scope of the invention to such catalysts.
[0012] Ziegler-Natta catalyst systems are generally formed from the
combination of a metal component (e.g., a potentially active
catalyst site) with one or more additional components, such as a
catalyst support, a cocatalyst and/or one or more electron donors,
for example.
[0013] A specific example of a Ziegler-Natta catalyst includes a
metal component generally represented by the formula: MR.sub.x;
wherein M is a transition metal, R is a halogen, an alkoxy, or a
hydrocarboxyl group and x is the valence of the transition metal.
For example, x may be from 1 to 6.
[0014] The transition metal may be selected from Groups IV through
VIB (e.g, titanium, chromium or vanadium), for example. R may be
selected from chlorine, bromine, carbonate, ester, or an alkoxy
group in one embodiment. Examples of catalyst components include
TiC4, TiBr.sub.4, Ti(OC.sub.2H.sub.5).sub.3C1,
Ti(OC.sub.3H.sub.7).sub.2C1.sub.2,
Ti(OC.sub.6H.sub.13).sub.2C1.sub.2,
Ti(OC.sub.2H.sub.5).sub.2Br.sub.2 and
Ti(OC.sub.12H.sub.25)C1.sub.3, for example.
[0015] Those skilled in the art will recognize that a catalyst may
be "activated" in some way before it is useful for promoting
polymerization. As discussed further below, activation may be
accomplished by contacting the catalyst with an activator, which is
also referred to in some instances as a "cocatalyst." Embodiments
of such Z-N activators include organoaluminum compounds, such as
trimethyl aluminum (TMA), triethyl aluminum (TEA1) and triisobutyl
aluminum (TiBAI), for example.
[0016] The cocatalyst is generally added to the process and/or the
catalyst in an amount defined as the cocatalyst ratio. As used
herein, the term "cocatalyst ratio" is generally defined as the
weight of cocatalyst (e.g., in lbs) divided by 1000 lbs of monomer.
Specifically, the cocatalyst ratio (described herein as the TEAL
cocatalyst ratio) described in the particular embodiments herein
refer to the weight of TEA1 cocatalyst (15 wt.% in hexane) divided
by 1000 lbs of monomer. The conventional TEAL cocatalyst ratio may
be from about 0.4 to about 1.6, or from about 0.5 to about 1.4 or
from about 0.8 to about 1.3.
[0017] However, embodiments of the invention (which may or may not
be utilized in combination with other embodiments described herein)
may include utilizing a cocatalyst ratio that is lower than
previously utilized. Such embodiments include a cocatalyst ratio
that is from about 15% to about 30% lower than that of an identical
conventional process (e.g., from about 0.3 to about 0.7). While
discussed herein in terms of TEA1 cocatalysts, it is contemplated
that other cocatalysts or combinations of catalyst may be utilized
in amounts that are from about 15% to about 30% lower than that
known to one skilled in the art. Such a reduction in the cocatalyst
ratio results in a reduction in the residual level (discussed in
further detail below and used interchangeably with catalyst
residual level and residual metals level), while maintaining
sufficient catalyst activity. For example, the residual metal level
in the polymer (e.g., aluminum) may be reduced by from about 15% to
about 30%.
[0018] The Ziegler-Natta catalyst system may further include one or
more electron donors, such as internal electron donors and/or
external electron donors. Internal electron donors may be used to
reduce the atactic form of the resulting polymer, thus decreasing
the amount of xylene soluble material in the polymer. The internal
electron donors may include amines, amides, esters, ketones,
nitriles, ethers, phosphines, diethers, succinates, phthalates, or
dialkoxybenzenes, for example. (See, U.S. Patent No. 5,945,366 and
U.S. Patent No. 6,399,837, which are incorporated by reference
herein.)
[0019] External electron donors may be used to further control the
amount of atactic polymer produced. The external electron donors
may include monofinctional or polyfunctional carboxylic acids,
carboxylic anhydrides, carboxylic esters, ketones, ethers,
alcohols, lactones, organophosphorus compounds and/or organosilicon
compounds. In one embodiment, the external donor may include
diphenyldimethoxysilane (DPMS), cyclohexymethyldimethoxysilane
(CMDS), diisopropyldimethoxysilane (DIDS) and/or
dicyclopentyldimethoxysilane (CPDS), for example. The external
donor may be the same or different from the internal electron donor
used.
[0020] The components of the Ziegler-Natta catalyst system (e.g.,
catalyst, activator and/or electron donors) may or may not be
associated with a support, either in combination with each other or
separate from one another. The Z-N support materials may include a
magnesium dihalide, such as magnesium dichloride or magnesium
dibromide, or silica, for example.
[0021] The Ziegler-Natta catalyst may be formed by any method known
to one skilled in the art. For example, the Ziegler-Natta catalyst
may be formed by contacting a transition metal halide with a metal
alkyl or metal hydride. (See, U.S. Pat. No. 4,298,718, U.S. Pat.
No. 4,298,718, U.S. Pat. No. 4,544,717, U.S. Pat. No. 4,767,735,
and U.S. Pat. No. 4,544,717, which are incorporated by reference
herein.)
Polymerization Processes
[0022] As indicated elsewhere herein, catalyst systems are used to
form polyolefin compositions. Once the catalyst system is prepared,
as described above and/or as known to one skilled in the art, a
variety of processes may be carried out using that composition. The
equipment, process conditions, reactants, additives and other
materials used in polymerization processes will vary in a given
process, depending on the desired composition and properties of the
polymer being formed. Such processes may include solution phase,
gas phase, slurry phase, bulk phase, high pressure processes or
combinations thereof, for example. (See, U.S. Pat. No. 5,525,678,
U.S. Pat. No. 6,420,580, U.S. Pat. No. 6,380,328, U.S. Pat. No.
6,359,072, U.S. Pat. No. 6,346,586, U.S. Pat. No. 6,340,730, U.S.
Pat. No. 6,339,134, U.S. Pat. No. 6,300,436, U.S. Pat. No.
6,274,684, U.S. Pat. No. 6,271,323, U.S. Pat. No. 6,248,845, U.S.
Pat. No. 6,245,868, U.S. Pat. No. 6,245,705, U.S. Pat. No.
6,242,545, U.S. Pat. No. 6,211,105, U.S. Pat. No. 6,207,606, U.S.
Pat. No. 6,180,735 and U.S. Pat. No. 6,147,173, which are
incorporated by reference herein.)
[0023] In certain embodiments, the processes described above
generally include polymerizing olefin monomers to form polymers.
The olefin monomers may include C.sub.2 to C.sub.30 olefin
monomers, or C.sub.2 to C.sub.12 olefin monomers (e.g., ethylene,
propylene, butene, pentene, methylpentene, hexene, octene and
decene), for example. Other monomers include ethylenically
unsaturated monomers, C.sub.4 to C.sub.18 diolefins, conjugated or
nonconjugated dienes, polyenes, vinyl monomers and cyclic olefins,
for example. Non-limiting examples of other monomers may include
norbomene, nobomadiene, isobutylene, isoprene,
vinylbenzocyclobutane, sytrene, alkyl substituted styrene,
ethylidene norbomene, dicyclopentadiene and cyclopentene, for
example. The formed polymer may include homopolymers, copolymers or
terpolymers, for example.
[0024] Slurry phase processes generally include forming a
suspension of solid, particulate polymer in a liquid polymerization
medium, to which monomers and optionally hydrogen, along with
catalyst, are added. The suspension (which may include diluents)
may be intermittently or continuously removed from the reactor
where the volatile components can be separated from the polymer and
recycled, optionally after a distillation, to the reactor. The
liquefied diluent employed in the polymerization medium may include
a C.sub.3 to C.sub.7 alkane (e.g., hexane or isobutane), for
example. The medium employed is generally liquid under the
conditions of polymerization and relatively inert. A bulk phase
process is similar to that of a slurry process. However, a process
may be a bulk process, a slurry process or a bulk slurry process,
for example.
[0025] In a specific embodiment, a slurry process or a bulk process
may be carried out continuously in one or more loop reactors. The
catalyst, as slurry or as a dry free flowing powder, may be
injected regularly to the reactor loop, which can itself be filled
with circulating slurry of growing polymer particles in a diluent,
for example. Optionally, hydrogen may be added to the process, such
as for molecular weight control of the resultant polymer. The loop
reactor may be maintained at a pressure of from about 27 bar to
about 50 bar or from about 35 bar to about 45 bar and a temperature
of from about 38.degree. C to about 121.degree. C, for example.
Reaction heat may be removed through the loop wall via any method
known to one skilled in the art, such as via a double-jacketed
pipe.
[0026] Alternatively, other types of polymerization processes may
be used, such as stirred reactors in series, parallel or
combinations thereof, for example. Upon removal from the reactor,
the polymer may be passed to a polymer recovery system for further
processing, such as addition of additives and/or extrusion, for
example.
[0027] The polymerization processes may further include contacting
the polymer with a catalyst quench agent. As used herein, the term
"quench agent" refers to a compound capable of terminating a
polymerization reaction. Such quench agents may include a compound
such as alcohols or water, for example.
[0028] Contact with the quench agent may occur at any time or in
any manner known to one skilled in the art. For example, such
contact may occur during the polymerization process prior to
removal of the polymer therefrom or may occur upon removal of the
polymer from the polymerization process, for example.
[0029] Unfortunately, the formed polymers include a level of metals
(i.e., residual level) resulting from catalyst system residues. For
example, these metals may include aluminum, magnesium or titanium,
for example. As used herein, the term "residual level"generally
refers to the aggregate level of residual metals present in the
polymer. Particular metal residual levels are referred to herein as
such, e.g., aluminum residual level.
[0030] While the residual level may be acceptable for some
applications, certain applications require a residual level that is
lower than that achieved by conventional processes. For example,
the formed polymers may include at least about 2 ppm of Mg, at
least 20 ppm of Cl, at least 30 ppm of Cr and/or at least 30 ppm of
Al.
[0031] Embodiments of the invention include utilizing monomer
(e.g., propylene for polypropylene) soluble alcohols, such as
isopropanol (IPA), as the quench agent. Unexpectedly, such contact
results in a reduction in residual levels compared to embodiments
utilizing other compounds as the quench agent. For example, the
aluminum residual level may be reduced to about 40 ppm or less.
[0032] Polymerization processes may further include contacting the
polymer with a washing agent. Such contact may occur by any method
known to one skilled in the art, such as in a wash column, for
example. In one embodiment, the washing agent contacts the polymer
in a flow that is countercurrent to the flow of the polymer.
[0033] One or more embodiments include utilizing additional monomer
(e.g., propylene for polypropylene) as the wash agent. The
additional monomer may contact the polymer in an amount that is
from about 0% to about 25% of the additional monomer feed rate, for
example. In addition, the additional monomer may contact the
polymer for a time of from about 10 minutes to about 15 minutes,
for example.
Polymer Product
[0034] The polymers (and blends thereof) formed via the processes
described herein may include, but are not limited to, linear low
density polyethylene, elastomers, plastomers, high density
polyethylenes, low density polyethylenes, medium density
polyethylenes, polypropylene (e.g., syndiotactic, atactic and
isotactic) and polypropylene copolymers, for example.
[0035] The polymers (and blends thereof) formed via one or more of
the embodiments described herein result in an unexpected reduction
in residual metals compared to processes not employing such
embodiments. For example, the polymers may include an aggregate
residual level of about 60 ppm or less, or 50 ppm or less, or 40
ppm or less, or 32 ppm or less or 25 ppm or less. The polymers may
further include an aluminum residual level of about 40 ppm or less,
or about 35 ppm, or about 30 ppm or less, or about 25 ppm or less
or about 20 ppm or less, for example.
[0036] In one embodiment, the polymers include polypropylene. The
propylene polymers may have a melt index (MI) of from about 0.01
dg/min to about 1000 dg/min., or from about 0.01 dg/min. to about
100 dg/min., or from about 0.02 dg/min. to about 50 dg/min., or
from about 0.03 dg/min. to about 10 dg/min. or from about 3.0 to
about 5.0, for example. As used herein, "melt flow index" is
measured via ASTM-D-1238-E. Unless otherwise designated herein, all
testing methods are the current methods at the time of filing.
[0037] The propylene polymers may further have a melting point of
at least about 125.degree. C, or from about 125.degree. C to about
170.degree. C or from about 150.degree. C to about 167.degree. C,
for example.
[0038] In addition, the propylene polymers may hold about 6 wt.% or
less, or about 5 wt.% or less or about 4 wt.% or less of xylene
soluble material, for example.
Product Application
[0039] The polymers and blends thereof are useful in applications
known to one skilled in the art, such as forming operations (e.g.,
film, sheet, pipe and fiber extrusion and co-extrusion as well as
blow molding, injection molding and rotary molding). Films include
blown or cast films formed by co-extrusion or by lamination useful
as shrink film, cling film, stretch film, sealing films, oriented
films, snack packaging, heavy duty bags, grocery sacks, baked and
frozen food packaging, medical packaging, industrial liners, and
membranes, for example, in food-contact and non-food contact
application. Fibers include melt spinning, solution spinning and
melt blown fiber operations for use in woven or non-woven form to
make filters, diaper fabrics, medical garments and geotextiles, for
example. Extruded articles include medical tubing, wire and cable
coatings, geomembranes and pond liners, for example. Molded
articles include single and multi-layered constructions in the form
of bottles, tanks, large hollow articles, rigid food containers and
toys, for example. In one embodiment, the polymers are used in
opaque film applications.
[0040] In particular, the polymers (and blends thereof) formed via
the embodiments described herein are useful in applications
requiring a reduced residual level. For example, the polymers are
useful in opaque film applications, such as food packaging,
cigarette wrapping, stationary lamination, shrink wrap and
industrial laminates, for example. The reduced residual level in
the polymer generally results in reduced degradation during the
film production process.
Example
[0041] In the following examples, samples of polypropylene were
produced.
[0042] All polymerizations included contacting propylene monomer
with a Ziegler-Natta catalyst within a loop reaction vessel to form
polypropylene having a melt flow of 2.8 g/10 min and a xylene
solubles content of 2.5 wt.%. The polymerization further included
introducing TEA1 (15in hexane) as cocatalyst into the reaction
vessel. The cocatalyst ratio of each run is shown in the table
below.
[0043] Each polymerization further included utilizing isopropyl
alcohol to quench the polymerization reaction further included
passing the polypropylene through a wash column. Propylen monomer
was also added to the wash column at a rate of 14,000 lb/hr.
TABLE-US-00001 TABLE 1 Sample Cocatalyst Ratio Al (ppm) Mg (ppm) 1
0.7 32.3 5.96 2 0.7 34.2 5.15 3 0.65 26.8 8.77 4 0.65 24.3 8.66 5
0.65 26.3 8.55 6 0.65 33.3 7.99
[0044] Unexpectedly, the production process improvements of the
present invention successfully result in a reduced residual level
of less than 40 parts per million in the final polyproplene
product. In particular, utilizing isopropyl alcohol as the quench
agent resulted in a polymer monomer aluminum residual level of less
than 40 ppm. Further, washing the polymer with proylene monomer
resulted in a further reduction of the aluminum residual level of
about 20%.
[0045] while the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof and
the scope thereof is determined by the claims that follow.
* * * * *